Over the course of four major arcs, Bleach has accumulated at least a hundred unique characters, nearly all of whom play memorable roles in the story. While the shinigami are generally considered to be the heroes, they sometimes make patently un-heroic decisions, even without any external provocation.
On the other hand, Bleach villains tend to be overly crude and violent, displaying an eerie sense of pride in their so-called "wicked" behavior, but this doesn't mean that every antagonist in the anime is teeming with malicious intent. Between the rigid anime concepts of heroism and villainy, however, exists a vast gray area where the lines of morality become blurred—more than a few characters inhabit this zone.
Acted Like A Villain — Shinji Hirako
Shinji's oily charm is far from endearing, especially when he pretends to be Ichigo's classmate despite being hundreds of years old. In fact, the gang suspects his intentions from the very outset because Shinji would rather attack Ichigo than explain the situation to him.
To make matters worse, he then reveals himself to be a Vizard: a Hollow-tainted shinigami. At this point, Shinji seems a lot creepier than most villains in Bleach.
Acted Like A Hero — Jugram Haschwalth
Jugram Haschwalth is Yhwach's right-hand man until he's betrayed by an unexpected Auswählen. While it is too late for him to obtain redemption, Haschwalth's final act partially compensates for the mistakes he has made in his life.
He exchanges his injuries with Uryuu, allowing the latter to take on Yhwach at full strength. Haschwalth may not be a hero, but he doesn't deserve such a fate just because he's a villain.
Acted Like A Villain — Suì-Fēng
Suì-Fēng is dedicated to her vision of the world, so much so that she considers any threat to it a personal affront. She despises Urahara because she believes that he has led Yoruichi astray, conveniently forgetting that the former two have been friends a lot longer than Suì-Fēng has been alive.
She can be a bit problematic at times, too, like when she cruelly wallops her vice-captain as a joke, or when she takes the sukeban trope too far.
Acted Like A Hero — Ulquiorra Cifer
A fan-favorite villain, Ulquiorra coldly torments and abuses Orihime and Ichigo, mocking them for feeling emotions as if being dead inside is a positive character trait.
However, the Espada eventually acknowledges that the absence of cardiac tissue doesn't mean he doesn't have a "heart," a personality change that is both surprising and refreshing. Ulquiorra's crimes as a Hollow notwithstanding, his wordless apology means everything to Orihime.
Acted Like A Villain — Byakuya Kuchiki
Byakuya Kuchiki hasn't always been the lovable scamp he is now, relatively speaking. He is brought in as the main antagonist of the Soul Society arc (the first major plotline in Bleach and one of the most popular).
Although Aizen is inevitably uncovered as the real puppet master behind Rukia's execution, Byakuya's insistence on protocol nearly gets his beloved sister killed. It's a good thing Ichigo pops in to knock some sense into him.
Acted Like Heroes — The Tres Bestias
The Tres Bestias are Tier Harribel's Fracción" Emilou Apacci, Franceska Mila Rose, and Cyan Sung-Sun—minor villains who are utterly defeated by Yamamoto in the Fake Karakura Town arc.
They aren't technically villains because their association with Aizen is through the Third Espada, a fact highlighted when they defend Hueco Mundo against Quilge Opie's invasion. The Tres Bestias even try to defeat the Quincy with all their might, forming a temporary alliance with Ichigo & co. in the process.
Acted Like A Villain — Zaraki Kenpachi
Kenpachi's bloodthirstiness is unparalleled, making him the most brutal combatant in the three known dimensions. He is barely kept under Soul Society's control by the Central 46, since the organization believes that Kenpachi has the innate power necessary to become a villain.
It's obvious that the 11th Squad captain isn't levelheaded when it comes to battle, but his close relationship with Soul Society ensures that he'll never stop fighting for them. Unless he gets bored with all the bureaucracy.
Acted Like A Hero — Coyote Starrk
Coyote Starrk is one-half of the greatest Vasto Lorde that ever lived; his partner being Lilynette Gingerbuck. Aizen grants him the prestigious position of Primera Espada, something Starrk grudgingly accepts out of loyalty (but not out of interest).
He's the second-most powerful villain in the Fake Karakura Town arc, but still prefers to settle matters without a fight. Further, Starrk and Shunsui, the shinigami who kills him, share a lot of similarities, implying that the Espada isn't all that bad, after all.
Acted Like A Villain — Mayuri Kurotsuchi
It's hard to imagine the scheming Mayuri Kurotsuchi as a hero, even though he's quite clearly one. This is because his attitude towards other living things is steeped in cold indifference—people's suffering doesn't matter to him as long as his experiments bear fruit.
Nearly all of Mayuri's battles involve some form of physical, emotional, psychological, and, in Hitsugaya's case, spatiotemporal torture. What's worse is the rictus of pleasure that appears on Mayuri's face when he leads his opponents to their miserable deaths.
Acted Like A Hero — Liltotto Lamperd
Litotto's schrift, The Glutton, is terrifying to behold—her mouth expands to bizarre proportions and takes a huge bite out of her victims. On the contrary, she doesn't really exhibit many villainous characteristics, especially considering how loyal she is to her Sternritter friends.
In fact, Liltotto tries to take revenge on Yhwach for abandoning his minions and stealing their powers. It doesn't go well for her, but at least she tries to set things right.